Ceramic insert into a composite slip segment

ABSTRACT

In composite slips and downhole tools using composite slips, there are provided one or more slip segments. The slip segments comprise a body and one or more inserts. The body is a composite material having an outer surface. The inserts each have an upper surface and each of the inserts is mechanically affixed into the body such that the upper surface of each of the inserts extends at least partially out from the outer surface. In some embodiments, the inserts are oval or stadium shaped and have a shoulder that locks the insert from moving by interaction with a shoulder in a cavity wall of the body.

FIELD

This invention relates generally to downhole tools for use in oil and gas wellbores and methods of anchoring such apparatuses within the casing of the wellbore. This invention particularly relates to the engagement of the slip elements within a casing or tubing. These slip elements are commonly used in setting or anchoring a downhole drillable packer, bridge plug and frac plug tools.

BACKGROUND

In drilling or reworking oil wells, many varieties of downhole tools are used. For example, but not by way of limitation, it is often desirable to seal tubing or other pipe in the casing of the well by pumping cement or other slurry down the tubing, and forcing the slurry around the annulus of the tubing or out into a formation. It then becomes necessary to seal the tubing with respect to the well casing and to prevent the fluid pressure of the slurry from lifting the tubing out of the well, or for otherwise isolating specific zones in a well. Downhole tools referred to as packers, bridge plugs and frac plugs are designed for these general purposes, and are well known in the art of producing oil and gas.

Both packers and bridge plugs are used to isolate the portion of the well below the packer or bridge plug from the portion of the well thereabove. Accordingly, packers and bridge plugs may experience a high differential pressure, and must be capable of withstanding the pressure so that the packer or bridge plug seals the well, and does not move in the well after being set.

Packers and bridge plugs both make use of metallic or non-metallic slip assemblies, or slips, that are initially retained in close proximity to a mandrel. These packers and bridge plugs are forced outwardly away from the mandrel upon the downhole tool being set to engage a casing previously installed within an open wellbore. Upon positioning the downhole tool at the desired depth, or position, a setting tool or other means of exerting force, or loading, upon the downhole tool forces the slips to expand radially outward against the inside of the casing to anchor the packer, or bridge plug, so that the downhole tool will not move relative to the casing. Once set, additional force, in the form of increased hydraulic pressure, is commonly applied to further set the downhole tool. Unfortunately, the increased pressure commonly causes the downhole tool to slip up or down the casing.

To prevent slipping of the downhole tool, cylindrically shaped inserts, or buttons, have been manually inserted and glued into pre-formed slip segments to enhance the ability of the slip segments to engage the well casing. The buttons must be of sufficient hardness to be able to partially penetrate, or bite into the surface of the well casing, which is typically steel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a downhole tool disposed in a well with a slip assembly.

FIG. 2 is a perspective view of a slip ring in accordance with one embodiment of the current disclosure.

FIG. 3 is a perspective view of one of the slip segments of a slip ring in accordance with the embodiment of FIG. 2.

FIG. 4 is a side cross-sectional view of a slip segment along line 4-4 of FIG. 3.

FIG. 5 is a top view of an insert suitable for use in the slip segment of FIGS. 3 and 4.

FIG. 6 is a side cross-sectional view of the insert taken along line 6-6 of FIG. 5.

FIG. 7 is an enlargement of a section of FIG. 6.

DETAILED DESCRIPTION

The present disclosure may be understood more readily by reference to the following detailed description as well as to the examples included therein. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, those of ordinary skill in the art will understand that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The figures are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the present disclosure.

Referring to the drawings, FIG. 1 illustrates well 10 having wellbore 12 with casing 14 cemented therein. Casing 14 has an inner wall 16. Downhole tool 18 includes mandrel 20 with an outer surface 22 and an inner surface 24.

By way of a non-limiting example, downhole tool 18 illustrated in FIG. 1 is referred to as a packer, and allows fluid communication therethrough. The packer illustrated may be used as a frac plug. In another non-limiting example, the downhole tool can also be a bridge plug, which can have a plug that seals off fluid flow through mandrel 20.

A spacer ring 32 is mounted to mandrel 20 with a pin 34. Slip assembly 36 is positioned on and/or disposed about mandrel 20. Spacer ring 32 provides an abutment, which serves to axially retain slip assembly 36. As illustrated, downhole tool 18 has two slip assemblies 36, namely a first slip assembly and second slip assembly, depicted in FIG. 1 as first and second slip assemblies 36 a and 36 b for ease of reference. Slip assemblies 36 a and 36 b provide anchoring for downhole tool 18 to casing 14 within well 10. The structure of slip assemblies 36 a and 36 b is typically identical, and only the orientation and position on downhole tool 18 are different. Each slip assembly 36 includes at least one slip ring 38 and at least one slip wedge 40. Slip ring 38 has an inclined/wedge-shaped first surface 42 positioned proximate to an inclined/wedge-shaped complementary second surface 44 of slip wedge 40. Slip assembly 36 is depicted as being pinned into place with pins 46.

Slip assemblies 36 a and 36 b are illustrated in FIG. 1 as being separated by packer element assembly 62. As illustrated, packer element assembly 62 includes at least one expandable packer element 64, which is positioned between slip wedges 40. Packer shoes 66 may provide axial support to the ends of packer element assembly 62.

In FIG. 1, downhole tool 18 is shown in its expanded or set position wherein slip rings 38 are radially expanded to be in contact with casing 14. Also, expandable packer element 64 is radially expanded to be in contact with casing 14. When introduced into wellbore 12, downhole tool 18 is in its unset position in which slip rings 38 and expandable packer element 64 do not contact the casing 14.

Slip ring 38, shown in FIG. 2, is an expandable slip ring 38 and has a plurality of slip segments 48. Collectively, all slip segments 48 make up a circumferential slip ring 38 wherein each slip segment 48 has a first side 70 and a second side 72 opposite to or opposing first side 70 such that first side 70 of one slip segment faces or is in contact with the second side 72 of another of the slip segments. Generally, the slip segments will have a frangible connection with each other so as to form slip ring 38. As illustrated in FIG. 2, slip ring 38 has eight slip segments 48. Slip ring 38 also has first or top end 74 and second or bottom end 76. First end 74 is adapted to receive slip wedge 40.

In one embodiment, slip segments 48 are separated by a groove 50, which is also a fracture channel 52. Groove 50 and fracture channel 52 are longitudinally or axially positioned between slip segments 48 and provide a weakened point in slip ring 38 for slip segments 48 to break apart from each other when sufficient forces are radially exerted on the interior of slip ring 38. Thus, the slip segments are frangibly connected together and the slip segments will separate along groove 50 when a predetermined radial force is applied. Preferably, slip ring 38 has at least one circumferential pair of slip segments 48 with at least one fracture channel 52 positioned therebetween. If fracture channels 52 are used to frangibly connect slip segments 48, then the slip ring 38 can be molded as a single integral unit with each slip segment 48 and fracture channels 52 being formed during the molding process. Thus, slip ring 38 is a one-piece or unitary slip ring.

Alternatively, slip segments 48 can be frangibly connected together by using adhesive along facing sides 70, 72 of adjacent slip elements 38. Additionally or alternatively to the adhesive and/or the fracture channels 52, restraining bands (not shown) can be placed in channels 78 and 80 to frangibly connect slip segments 48 together. Channels 78, 80 extend across each slip segment 48 so that, when slip segments 48 form slip ring 38, channels 78, 80 extend circumferentially about slip ring 38.

In some embodiments, a pin (not shown) is used to hold slip segments 48 in place on mandrel 20. The pins can be used alone or with fracture channel 52, an adhesive at first and second sides 70, 72, and/or retaining bands in channels 78, 80, to provide a frangible connection of slip segments 48 into slip ring 38. If used, the pin extends through pinhole 81 in slip segment 48 and is secured into mandrel 20.

If fracture channels 52 are not used to frangibly connect slip segments 48, then slip elements 48 can be separately molded and then assembled into slip ring 38 by frangible connections.

When downhole tool 18 is in its unset position, slip elements 48 will be frangibly connected, as described above, to form slip ring 38. When downhole tool 18 is in its set position, the frangible connection of slip element 48 will be broken so that slip elements 48 can separate and move outward towards casing 14.

As best seen from FIGS. 3 and 4, each slip segment 48 comprises a body 82 of composite material and one or more inserts 84. Each insert 84 is molded into a slip segment 48 so as to be retained in the slip segment and partially extend outward from body 82. As can be seen from FIGS. 3 and 4, upper surface 86 of insert 84 extends at least partially out from outer surface 83 of body 82. Typically, upper surface 86 extends from a first edge 88 adjacent to outer surface 83 of body 82 to a second edge 90 that is outward from the outer surface such that the upper surface extends out from the outer surface at an angle α. Generally, angle α is from about 5 degrees to about 45 degrees. Alternatively, angle α can be from about 10 degrees to about 30 degrees or from about 12 degrees to about 20 degrees.

Inserts 84 generally comprise a material having sufficient hardness to bite or penetrate into casing 14 when downhole tool 18 is moved to its set position and slip segments 48 are expanded outward, as shown in FIG. 1. For example, inserts 84 can be made from a material selected from the group consisting of tungsten carbide, metals, ceramic and combinations thereof. Metals can be selected from the group consisting of iron, steel, nickel, molybdenum, and combinations thereof. Ceramics can generally include ceramic oxides, ceramic carbides and ceramic nitrides. More typically, ceramics can be selected from the group consisting of metallic-ceramic, zirconia ceramic, silicon nitride ceramics, zirconia-ceramic titanium and combinations thereof.

In the past, circular buttons have been used as inserts and were glued into apertures in the body of a slip segment. Advantageously, the current inserts are designed so as to allow for mechanically affixing or fastening the inserts in the body of the slip segment so as to more securely attach the insert with a more cost-effective production of the slip segment. As used herein, “mechanically affixing” or “mechanically fastening” refers to mechanical joining using a force or form locking method like integral joints, seams, crimps, clinching, shrink-fits or custom molding. Generally preferred are form locking methods like integral joints, shrink fits or custom molding. As used herein, “custom molding” refers to molding so as to form an integral joint between the inserts and body or to create a form locking between the inserts and body. Molding the inserts into composite slip bodies is a different method of installation resulting in an improved slip segment than prior art slip segment manufacturing processes. Also, such molding results in a reduction of costly preparation steps and a slip segment having a more secure insert with less change of unwanted separation of the insert from the composite slip body. Additionally, mechanical affixing which does not rely on the use of adhesives, or similar chemical methods of bonding, is typically preferred.

Turning now to FIGS. 5-7, an insert 84 in accordance with one embodiment can be seen. Insert 84 comprises upper surface 86, lower surface 92 and a sidewall 94. Sidewall 94 extends from lower surface 92 to upper surface 86. As illustrated in FIG. 5, sidewall 94 is configured such that a cross-section taken perpendicular to the sidewall has an elongate shape, such as an oval shape. Preferably, the side cross-section has a stadium shape, also known as a discorectangle and obround. A stadium is a two-dimensional geometric shape constructed of a rectangle with semicircles at a pair of opposite sides, typically the shorter two sides of the rectangle.

In some embodiments, sidewall 94 has a base portion 96, a top portion 98 and an angular portion 100. Base portion 96 extends from lower surface 92 to angular portion 100, and top portion 98 extends from angular portion 100 to upper surface 86. All three portions have a cross-section which is an elongated shape and which is generally an oval shape and more typically a stadium. Base portion 96 has a larger perimeter 97 than perimeter 99 of top portion 98 (see FIG. 5). Angular portion 100 connects the bottom and top portions so as to form a shoulder 102 around the perimeter of sidewall 94 which angles from base portion 96 to top portion 98 and thus provides a transition from the larger perimeter 97 to the smaller perimeter 99. Generally, the perimeter can be at an angle β with respect to a line 104 perpendicular to the surface of base portion 96, as illustrated in FIG. 7. As used herein, an angle β will sometimes be referred to as the angle from the base portion. Angle β, or the angle from the base portion, broadly can be from almost −90 degrees to almost 90 degrees where values of between −90 degrees and 0 degrees represent angular portion 94 cutting back into insert 84 to form a channel around sidewall 94 (not shown in the pictures). More preferably, for a strong locking mechanism, angle β can be between from about −60 degrees to about 80 degrees. More typically, angle will be greater than about −10 degrees or will be at least about 0 degrees, at least about 20 degrees, or at least about 30 degrees. Typically, angle β will be at most about 80 degrees, at most about 75 degrees, at most about 60 degrees, or at most about 50 degrees. Sometimes angle β will be about 45 degrees.

Returning to FIG. 4, it is currently preferred that body 82 is configured to mechanically affix insert 84. As shown, body 82 is formed with a cavity wall 106, which defines a cavity 108 in body 82. Cavity wall 106 is formed around insert 84 so that cavity 108 contains at least part of insert 84. In addition, the manufacturing process forms an opposing shoulder 110 along the surface of cavity wall 106. Opposing shoulder 110 faces or opposes shoulder 102 of insert 84 to thus lock insert 84 into position within body 82. That is, opposing shoulder 110 is in contact with and mates with shoulder 102 so as to lock insert 84 within the cavity 108.

The larger oval-shaped inserts and stadium-shaped inserts of the above embodiments provide for production composite slip bodies having the inserts mechanically affixed therein, whereas prior art inserts have a round cross-section, are smaller and require after molding attachment of the inserts, typically by using adhesives, which are subject to failure so as to allow the insert to fall out. The larger surface area of the current insert provides a better surface for the mold cavity to hold on to during the compression molding process. The shoulder provided by the angular portion around the perimeter of the insert results in an increased width of the bottom of the insert and allows the insert to be locked into position. Without this feature, it is possible for the insert to become dislodged from the slip. Generally, it is desirable for the mechanical affixing to result in a custom fit for cavity wall 106 to precisely match cavity 108 for each individual insert, enhancing the attachment of the insert in the slip segment. Further, oval-shaped or stadium-shaped inserts provide for more insert material to engage the casing wall once the slip segment has been forced outward toward the casing wall, than the traditional circular inserts.

The body is formed from a composite material, which typically comprises engineering grade plastics (preferably thermoplastics) and fibers. The fibers can be carbon fibers, fiberglass, or any other suitable fiber.

In operation, downhole tool 18 is introduced into the wellbore and casing 14. Downhole tool 18 is then positioned at the desired depth or location by a setting tool, such as a wireline. The wireline exerts an initial or setting force upon slip assembly 36, causing slip wedge 40 and slip ring 38 to move relative to one another, which exerts a radial force upon slip ring 38. Slip wedge 40 has inclined surface 44 defined thereon. Slip ring 38 radially expands outward as complementary surface 42 slides against inclined surface 42 of slip wedge 40. Generally, the radial expansion fractures the connection between slip segments 48; thus, slip segments 48 can move outward separately from each other. The sliding effect of complementary surface 42 against inclined first surface 44 causes each slip segment 48 to force second edge 90 of each of its insert 84 against casing inner wall 16. As the radial force is increased, second edge 90 bites into casing inner wall 16. As the force continues or increases, the remaining portion of insert 84 outside composite body 82 penetrates into casing inner wall 16.

Additionally, the application of the setting force causes slip wedges 40 to move towards each other, thus compressing expandable packer element 64. As expandable packer element 64 is compressed longitudinally, it expands radially and comes into sealing contact with casing inner wall 16. Once expandable packer element 64 is in sealing engagement with casing inner wall 16 and inserts 84 have penetrated into casing inner wall 16, downhole tool 18 is set.

Several alternative embodiments will now be set forth to further define the invention. In one group of embodiments, a composite slip comprises one or more slip segments. The slip segments comprise a body and one or more inserts. The body is a composite material having an outer surface. The inserts each have an upper surface and each of the inserts are mechanically affixed into the body such that the upper surface of each of the inserts extends at least partially out from the outer surface.

In another group of embodiments, a downhole tool comprises a mandrel and a slip assembly positioned on the mandrel. The slip assembly has at least one outwardly expandable slip ring and at least one slip wedge, wherein the slip wedge and slip ring are movable relative to one another when force is applied to the slip assembly. The slip ring will expand radially outward in response to such movement. The slip ring comprises a plurality of slip segments. The slip segments have a body of composite material having an outer surface, and one or more inserts. Each insert having an upper surface and each of the inserts are mechanically affixed into the body such the upper surface of each of the inserts extends at least partially out from the outer surface.

In some of the above embodiments, each of the inserts further comprises a lower surface and a sidewall. The sidewall has a perimeter and is shaped such that a cross-section taken perpendicular to the sidewall has an oval shape. The oval shape can be a stadium shape. Further, the sidewall can have a base portion, a top portion and an angular portion. The base portion has a larger perimeter than the top portion and the angular portion connects the bottom and top portions so as to form a shoulder around the perimeter of the sidewall. Generally, in such embodiments, the insert is mechanically affixed within the body so as to form a cavity wall defining a cavity in the body, wherein the cavity contains at least part of the insert and the cavity wall has an opposing shoulder to the shoulder around the perimeter of the sidewall to thus lock the insert into position within the body. The angular portion can be at an angle from about 0 degrees to about 80 degrees from the base portion. Alternatively, the angular portion can be at an angle from about 0 degrees to about 75 degrees, from about 20 degrees to about 60 degrees, from about 30 degrees to about 50 degrees, or about 45 degrees from the base portion.

In some embodiments, the upper surface of each of the inserts extends from a first edge adjacent to the outer surface to the body to a second edge that is outward from the outer surface such that the upper surface extends out from the outer surface at an angle from about 5 degrees to about 45 degrees to the outer surface. Alternatively, the upper surface can extend out from the outer surface at an angle from about 10 degrees to about 30 degrees or from about 12 degrees to about 20 degrees to the outer surface.

In some embodiments, the body has a plurality of the inserts mechanically affixed into the body. In some of these embodiments, the body has two inserts mechanically affixed into the body.

In still other embodiments, the composite slip comprises a plurality of the slip segments described above. Each slip segment has a first side and a second side opposing the first side with the first side of one slip segment contacted with the second side of another of the slip segments in a frangible connection so as to form a slip ring, which will separate upon application of a predetermined radial force.

Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed herein are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is, therefore, evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention.

While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods also can “consist essentially of” or “consist of” the various components and steps. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a to b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Additionally, where the term “about” is used in relation to a range it generally means plus or minus half the last significant figure of the range value, unless context indicates another definition of “about” applies.

Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an” as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent(s) or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted. 

What is claimed is:
 1. A composite slip comprising: one or more slip segments comprised of: a body of composite material having an outer surface; and one or more inserts with each insert having an upper surface, wherein each of the inserts are mechanically affixed into the body such the upper surface of each of the inserts extends at least partially out from the outer surface.
 2. The composite slip of claim 1, wherein each of the inserts further comprises a lower surface and a sidewall, wherein the sidewall has a perimeter and is shaped such that a cross-section taken perpendicular to the sidewall has an oval shape.
 3. The composite slip of claim 2, wherein the oval shape is a stadium shape.
 4. The composite slip of claim 3, wherein the sidewall has a base portion, a top portion and an angular portion, the base portion having a larger perimeter than the top portion and the angular portion connecting the bottom and top portions so as to form a shoulder around the perimeter of sidewall.
 5. The composite slip of claim 4, wherein the insert is mechanically affixed within the body so as to form a cavity wall defining a cavity in the body, wherein the cavity contains at least part of the insert and the cavity wall has an opposing shoulder to the shoulder around the perimeter of the sidewall to thus lock the insert into position within the body.
 6. The composite slip of claim 5, wherein the angular portion is at an angle from about 0 degrees to about 75 degrees from the base portion.
 7. The composite slip of claim 6, where the upper surface of each of the inserts extends from a first edge adjacent to the outer surface to the body to a second edge that is outward from the outer surface such that the upper surface extends out from the outer surface at an angle from about 5 degrees to about 45 degrees to the outer surface.
 8. The composite slip of claim 7, wherein the body has a plurality of the inserts mechanically affixed into the body.
 9. The composite slip of claim 7, wherein the body has only two inserts mechanically affixed into the body.
 10. The composite slip of claim 7, further comprising a plurality of the slip segments, wherein each slip segment has a first side and a second side opposing the first side with the first side of one slip segment contacted with the second side of another of the slip segments in a frangible connection so as to form a slip ring, which will separate upon application of a predetermined radial force.
 11. A downhole tool comprising: a mandrel; and a slip assembly positioned on the mandrel, the slip assembly having at least one outwardly expandable slip ring and at least one slip wedge, wherein the slip wedge and slip ring are movable relative to one another when force is applied to the slip assembly, and the slip ring will expand radially outward in response to such movement, and wherein the slip ring comprises a plurality of slip segments having: a body of composite material having an outer surface; and one or more inserts with each insert having an upper surface, wherein each of the inserts are mechanically affixed into the body such that the upper surface of each of the inserts extends at least partially out from the outer surface.
 12. The downhole tool of claim 11, wherein each slip segment has a first side and a second side opposing the first side with the first side of one slip segment contacted with the second side of another of the slip segments in a frangible connection so as to form the slip ring, which will separate upon movement of the slip wedge relative to the slip ring.
 13. The downhole tool of claim 12, wherein each of the inserts further comprises a lower surface and a sidewall, wherein the sidewall has a perimeter and is shaped such that a cross-section taken perpendicular to the sidewall has an oval shape.
 14. The downhole tool of claim 13, wherein the oval shape is a stadium shape.
 15. The downhole tool of claim 14, wherein the sidewall has a base portion, a top portion and an angular portion, the base portion having a larger perimeter than the top portion and the angular portion connecting the bottom and top portions so as to form a shoulder around the perimeter of the sidewall.
 16. The downhole tool of claim 15, wherein the insert is mechanically affixed within the body so as to form a cavity wall defining a cavity in the body, wherein the cavity contains at least part of the insert and the cavity wall has an opposing shoulder to the shoulder around the perimeter of the sidewall to thus lock the insert into position within the body.
 17. The downhole tool of claim 16, wherein the angular portion is at an angle from about 0 degrees to about 75 degrees from the base portion.
 18. The downhole tool of claim 17, where the upper surface of each of the inserts extends from a first edge adjacent to the outer surface to the body to a second edge that is outward from the outer surface such that the upper surface extends out from the outer surface at an angle from about 5 degrees to about 45 degrees to the outer surface.
 19. The downhole tool of claim 18, wherein the body has a plurality of the inserts mechanically affixed into the body.
 20. The downhole tool of claim 19, wherein the body has only two inserts mechanically affixed into the body. 